This explains why you can never remember where you left your car keys.

What did we ever do without them? Joshua Foer says that, before the invention of inexpensive printing, memory wasn’t just everything — it was the only thing. People with prodigious memories were the rock stars of their time.

So why can’t you remember to grab your lunch on the way out the door?

As it turns out, there’s a good excuse for your lapses. Psychologists say there’s a “curve of forgetting” that starts the second you learn something, and if there are more than seven components, the problem worsens. (Phone numbers are seven digits long for a reason.)

Foer went on a mission to find out how memory works. First he attended the U.S. Memory Championships, held every spring, where he found himself in a world of memory athletes who can memorize and repeat back (in order) thousands of random numbers, hundreds of shuffled playing cards, and thousands of words, names, and faces. And Foer discovered a surprising thing: Memory athletes aren’t nerds with photographic recall. Instead, they use the ancient memorization technique of associating items in random lists with unusual visual images and then “placing” those image clusters inside the “rooms” of large imaginary houses. (Then all you have to do is move from room to room in your mind, circling around the dining room, say, and recalling the facts that you’d linked in visual clusters.)

Part serious brain science, part history, and part rompish fun, Foer takes a peek inside our heads to learn why we have few strong memories of our toddler-hoods, what it’s like to live with a complete loss of short-term memory, why Malcolm Gladwell was right about practice, how scientists are trying to “see” memories in our brains, how our brains compensate for memory loss, and why you can recall your whereabouts on 9/11/01 but you don’t know where you left your glasses.

So if the old string-around-your-finger technique has failed you again, make a mental note and don’t forget this title: Moonwalking with Einstein.